Transmitter



J y 1 1 4 A. F. HORLACHER TRANSMITTER Filed y 1941 IZ IIIILY/ 2 no a 1} W i VIII/4111:1111!!! Il/A,

INVENTOR ALBERT F. HORLACHER I BY 0. f l g I ATTORNEYS.

atented July 18,1944

UNITED "STATES PATENT OFFICE TRANSMITTER Albert F. Horlacher, Genoa, Ill., asslgnor to Auto- .matic Electric Laboratories, Inc., a corporation of Delaware I Application my 9, 1941, Serial No. 401,592

11 Claims. (01. 179-422) The present invention relates to transmitters and more particularly to telephone transmitters.

A conventional telephone transmitter is responsive to sound waves of difierentfrequencies disposed within the audible range and including backgroundsound waves having frequencies disposed ,within a-first band in the-audible range and signal sound waves having frequencies dis- I posed in a second band in the audible-range.

Ordinarily; the background sounds or noises have frequencies disposed toward the lower end of the audible range; while the signal sounds have frequencies disposed toward the higher end of the audible range. Consequently, the telephone transmitter transmits sound energy corresponding both to the background noises and to the signal sounds, thereby to cause a telephone receiver associated with the telephone transmitter to reproduce both the background noises and the signal sounds.

Accordingly, it is an object of the present intransmitter embodying the present invention; and

Fig. 2 is a longitudinal-sectional view of the transmitter taken along the line 2-2 in Fig. 1.

Referring now moreparticularly to Figs. 1 and 2 of the drawing. there is shown a telephone transmitter III which comprises a hollow casing, including a cup-shaped member H provided with a cylindrical side wall l2 and an annular top wall ill, the exterior surface of the side wall l2 being threaded as indicated at H for reception in a suitable support, not shown. The casing also comprises a tubular member l5 constituting a bottom wall, the member l5 being provided with an outwardly extending annular flange l6.

Preferably, the cup-shaped member H and the tubular' member l2 are formed of a suitable aluminum alloy and are retained in assembled relation by an arrangement comprising two invention to provide a transmitter embodying an improved arrangement for preventing the transmitter from transmitting sound energy corresponding to the background noises.

Another object of the invention is to provide in a transmitter, an improved mechanical filter V arrangement for filtering out undesirable noises having frequencies disposed within a predeter mined :band in the audible range of the transmitter.

Another object of the invention is to provide a transmitter embodying an improved acoustic arrangement which is effective to increase the sound energy transmitted thereby within a predetermined band toward the low frequency end of the operating range thereof.

A further object of the invention is to provide in a transmitter, an improved acoustic-mechanical arrangement which is effective to produce a high degree of uniformity of response over the entire operating frequency range thereof. A further object of the invention is to provide a transmitter which is of simple and rugged structure and which is of compact and lightweight construction;

The novel features believed to be characteristic of the invention are set forth with particularity in the appended claims. The invention, both as to its organization and method of operation, togetherwith further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawing, in which Figure 1 is-a planview .of a telephone sulating rings I1 and I8 and a metallic ring l9. More particularly, the insulating ring I! is arranged within an annular recess I2a provided in the interior of the side wall l2 adjacent the end thereof, the insulating ring I! having an annular recess Ila therein receiving the annular flange V IS. The insulating ring I! is interposed between the annular flange I6 and the metallic ring 19,

whereby the tubular member l5 and the annular flange it carried thereby are electrically insulated from the side wall l2 of the cup-shaped member ll. Finally, the tubular member I5 is retained in place in a clamped condition between the insulating rings I1 and I8 due to pressure exerted by the metallic ring it, the metallic ring l9 being retained in place by a spun-over-bead I2b provided on the outer end of the side wall l2.

' Also; the transmitter 10 comprises upper and lower movable electrodes 20 and 2|, respectively. The upper electrode 20 has a cup-shaped configuration and is resiliently mounted within the casing of the transmitter ID by an arrangement comprising a first resilient member 22extending between the peripheral portion of he electrode 20 and an inwardly disposed and downwardly projecting flange 23 carried by'the top wall l3 of the member ll. Preferably, the resilient member 22 has a bellows-like construction and is formed of paper, the lower end of the resilient member 22 being sealed to'the adjacent peripheral portion of the electrode 20 and the upper end of the resilient member 22 being sealed to the lower face of the annular flange 23. The upper electrode 20 is arranged in spaced relation with respect to the top wall l3, whereby a first chamber 24 is defined withinthe casing of, the transmitter H! by the upper electrode 20, the resilient member 22, the annular flange 23 and the top wall l3.

Similarly, the lower electrode 2| has a cupshaped configuration and is resiliently mounted within the casing of the transmitter III by an 25 being sealed to the adjacent peripheral portion of the electrode 2| and the lower end of the resilient member 25 being sealed to the upper face of the annular flange 26. The tubular member I5 has an annular opening |5a formed therein, which is sealed by an annular plug 21, the plug 2 being sealed in place by aspun-over bead b provided on the outer end of the member IS. The lower electrode 2| is arranged in spaced relation with respect to the plug 21, whereby a second chamber 28 is defined within the casing of the transmitter ill by the lower electrode 2|, the resilient member 25, the annular flange 26, the member l5 and the plug 21.

The upper and lower electrodes and 2| are arranged in spaced relation and are connected together by a third resilient member 29 extending therebetween. Preferably, the resilient member 29 has a bellows-like construction and is formed of paper, the upper end of the resilient member 29 beingsealed to the adjacent peripheral portion of the up :r electrode 20 and the lower end of the resilient member 29 being sealed to the adjacent peripheral portion of the lower electrode 2|. The upper and lower electrodes 20 and 2| and the resilient member 29 cooperate to define a compartment 30 therebetween, which contains a quantityv of granulated carbon 3| constituting a variable impedance element. The central portionof the upper electrode 20 has an opening formed therein which is sealed by a suitable metallic plug '32. Similarly, the central portion of the lower electrode 2| has an opening formed therein which is sealed by a suitable metallic plug 33. Further it is noted that a metallic weight 34 is arranged within the second chamber 28 and secured to the lower electrode 2| by an arrangement comprising a screw 35. More particularly, the head of the screw 35' is arranged within a recess 34a provided in the weight 34, while the shank of the screw 35 is arranged in threaded engagement with respect to a tapped hole provided in the plug 33.

Preferably, the upper and lower electrodes 20' and 2|- are formed of a suitableelectrical conducting material, such as carbon, and are respectively electrically connected to the members H and [5, which members form the two electrical terminals of the transmitter i0. More particularly, the upper electrode 20 is electrically connected to the top wall |3 of the member II by a flexible conductor 36; and the lower electrode 2| is electrically connected to the member l5 by a flexible conductor 31 extending between the member l5 and the weight 34.

The sidewall |2,-the top wall l3, the insulating ring H, the annular flange IS, the annular flanges 23 and 26, the electrodes 20 and 2| and the resilient members 22, 25 and 29 cooperate to define. a third chamber 38 within the casing of the transmitter I0 disposed in surroundin relationship withrespect to the electrodes 20 and 2| and the chambers 24 and 28. Four annularly disposed openings 39 are formed in the top wall l3 and communicate between the exterior and the first chamber 24; while four annularly disposed openings 40 are formed in the top wall l3 and communicate between the exterior and the third chamber 38. Finally, a series of spaced-apart openings 4| are formed in the annular flange 26 and communicate between the second chamber 28 and the third chamber 38. Accordingly, the openings 39 provide a direct restricted passage between the exterior and the first chamber 24, whereby the movement of the upper electrode 20 may be controlled by sound-pressure waves; while the openings 40 and Al provide a series restricted passage through the third chamber 38 between the exterior and the second chamber 28, whereby the movement of the lower electrode 2| may be controlled by sound-pressure waves.

During the operation of the transmitter l0 the sound-pressure waves entering the first chamber 24 act upon the upper electrode 20 in order to cause vibration thereof; and the sound-pressure waves entering the second chamber 28 act upon the lower electrode 2| in order to cause vibration thereof, whereby the quantity of granulated carbon 3| disposed in the compartment 30 formed between the electrodes 2|l.and 2| is compressed to a degree determined by the relative movement of the electrodes 20 and 2| in order to vary the terminal impedance of the transmitter in accordance with the sound waves acting thereon. Preferably, the mass-stiffness of the lower electrode and its resilient mounting, as determined primarily by the stiffness of the resilient member 25, the mass of the electrode 2|, the plug 33, the weight 34 and the screw 35, is of such a value that the lower electrode 2| is .moved with the upper electrode 20 by forces acting through the quantity of granulated carbon 3| within a predetermined band toward the low frequency end of the operating range of the transmitter l0, whereby the relative movement between the upper and lower electrodes 20 and 2| is minimized in thepredetermined band mentioned in order to filter out background noises disposed within this frequency band. Also, the dimensions of the series passage communicating between the exterior and the second chamber 28, including the openings 40 and 4| and the third chamber 38, are so proportioned and related that it ofiers a relatively high impedance to the passage of sound-pressure waves within a given band toward the high frequency end of the operating range of the transmitter l0, whereby sound-pressure.

waves within the given band mentioned have a minimum action upon the lower electrode 2|, this series passage being efiectively blocked at frequencies within this frequency band.

In a preferred embodiment of the transmitter ID, the mass-stillness of the lower electrode 2| and its resilient mounting is of such a value that the lower electrode 2| has a fundamental resonance frequency of the order of 800 cycles per second; and the mass-stiffness of the upper electrode 20 and its resilient mountin islof such a value that the upper electrode 20 has a fundamental resonance frequency of the order of 1500 cycles per second. The value of the mass-stillness of the lower electrode 2| and its resilient mounting is determined primarily by the stiffness'of the resilient member 25 and the mass of the electrode 2|, the plug 33, the weight 34 and the screw 35., as previously noted; and may be per, the value of the mass-stiflness of the upper electrode 2| and its resilient mounting is determined primarily by the stiffness of the resilient member 22 and the mass of the upper electrode 20 and the plug 32. Also, the stiffness reactance of the first chamber 24 isso proportioned and related with respect to the mass reactance of the direct communicating passage, including the openings 39, that thelcolumn of air in the first chamber 24 has an effective resonance frequency of the order of 2500 cycles per second; while the stiffness reactance of the second chamber 28 is so proportioned and related with respect to the mass reactance of the series communicating passage, including the openings- 40 and 4| and the third chamber 38, that the columnof air in the second chamber 28 has an effective resonance frequency of the order of 3000 cycles per second. Accordingly, in the preferred embodiment of the transmitter ID, the output response characteristic thereof has four peaks occurring approximately at'800, 1500, 2500 and 3000 cycles per second due to the factors mentioned above.

Moreover, in the preferred embodiment of the transmitter ID, the mass-stiffness of the lower electrode 2| and its resilient mounting is of such a value that the lower electrode 2| is moved with the upper electrode 20 by forces acting through the quantity of granulated carbon 3| at frequencies disposed below a frequency of the order of 500 cycles per second, thereby to establish an effective cutoff point at this frequency such that low frequency background noises below the cutoff point are not transmitted by the transmitter l0. Finally, in the preferred embodiment of the transmitter l0, themass reactance of the series passage, including the openings 40 and and the third chamber 38, is of such a value that frequencies above a frequency of the order of 4000 cycles per second are trapped in the'third chamber 38 and not transmitted to the second chamber 28, whereby the lower electrode 2| is not materially acted upon by frequencies above a frequency of the order of 4000 cycles per second in the operating range of the transmitter l0.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention. 4

What isclaimed is:

l. A transmitter comprising a hollow casing,

first and second movable electrodes disposed ing a direct restricted passage between the exterior and said first chamber, whereby the movement of said first electrode may be controlled by sound-pressure waves, and second and third openings formed in said casing and providing a series restricted passage through said third chamber between the exterior andsaid second chamber, whereby the movement of said second silient member extending between said downwardly projecting flange and said upper electrode for supporting said upper electrode within said casing and cooperating therewith to define a first chamber within said casing, means including a second resilient member extending between said upwardly projecting flange and said lower electrode for supporting said lower electrode within said casing and cooperatin therewith to define a second chamber within said casing, a third resilient member extending between said electrodes and cooperating therewith to definea'compartment therebetween, a variable impedance element arranged within said compartment, the effective impedance of said element being governed in accordance with the relative movement between said electrodes, the side 'wall and the top and bottom walls of said casing cooperating with both of said flanges and both'of said electrodes and all three of said resilient elements-to siliently mounted within said 1 casing, a first chamber defined in said casing adjacent said within said casing, means including a first resilient member for supporting said first electrode within said casing and cooperating with said, firstelectrode and the walls of said casing to define a first chamber within said casing, means including a second resilient member for supporting said second electrode within said casing and cooperating with said second electrode and the walls of said casing to define a second chamber within said casing, a third resilient member extending'between said electrodes and cooperating therewith to define a compartment therebetween, a variable impedanceelement arranged within said compartment, the effective impedance of said element being governed in accordance with the relative movement between said electrodes, the walls of said casing cooperating with both of said electrodes and all three of said resilient elements to define a third chamber therein, a first opening formed in said casing and providfirst electrode, a second chamber defined in said casing adjacent said second electrode, a first re-- stricted passage formed in said casing and communicating between the exterior and said first chamber, whereby the movement of said first electrode may be controlled by sound-pressure waves, a second restricted passage formed in said casing and communicating between the exin accordance with the relative movement between said electrodes.

4. A transmitter comprising a hollow casing,-

a first movable electrode resiliently mounted within said casing, a second movable electrode resiliently mounted within said casing, a first chamber defined in said casing adjacent said first electrode, a second chamber defined in said casing adjacent said second electrode, a first restricted passage formed in said casing and communicating between the exterior and said first chamber, whereby the movement of said first electrode may be controlled by sound-pressure waves, a second restricted passage formed in said casing and communicating between the exterior and said second chamber, whereby the movement of said second electrode may be controlled by sound-pressure waves, the dimensions of said second passage being so proportioned and re- I first movable electrode resiliently mounted within said casing, a second movable electrode resiliently mounted within said casing, a first chamber defined in said casing adjacent said first electrode, a second chamber defined in said casing adjacent said second electrode, a first restricted passage formed in said casing and communicating between the exterior and said first chamber, whereby the movement of said first electrode may be controlled by sound-pressure waves, a second restricted passage formed in said casing and communicating between the exterior and said second chamber, whereby the movement of said second electrode may be controlled by sound-pressure waves, and a variable impedance element arranged between said electrodes, the effective impedance of said element being governed in accordance with the relative movement between said electrodes, the mass-stiffness of said second electrode and its resilient mounting being of such a value that said second electrode is moved with said first electrode by forces acting through said element at frequencies within a predetermined band in the operating range of the transmitter. p

6. A transmitter comprising a hollow casing, a first movable electrode resiliently mounted within said casing, a second movable electrode resiliently mountedwithin said casing, a first chamber defined in said casing adjacent said first electrode, a second chamber defined in said casing adjacent said second electrode, a first restricted passage formed in said casing and communicating between the exterior and said first chamber, whereby the movement of said first electrode may be controlled by sound-pressure waves, a second restricted passage formed in said casing and communicating between the exterior and said second chamber, whereby the movement of said second electrode may be controlled by sound-pressure waves, and a variable impedance element arranged between said electrodes, the effective impedance of said elementbeing governed in accordance with the relative movement between said electrodes, the massstiifness of said second electrode and its resilient mounting being of such a value that said second electrode is moved with said first electrode by forces acting through said element at frequencies within a predetermined band toward the low frequency end of the operating range of the transmitter.

7. A transmitter comprising a hollow casing, a first movable electrode resiliently mounted within said casing, a second movable electrode resiliently mounted within said casing, a first chamber defined in said, casing adjacent said first electrode, a second chamber defined in said casing adjacent said second electrode, a first restricted passage formed in said casing and communicating between the exterior and said first chamber, whereby the movement of said first electrode may be controlled by sound-pressure waves, a second restricted passage formed in said casing and communicating between the exterior and said second'chamber, whereby the movement of said second electrode may be controlled by sound-pressure waves, and a variable impedance element arranged between said electrodes, the efiective impedance of said element being governed inaccordance with the relative movement between said electrodes, the mass-stiffness of said second electrode and its resilient mounting being of such a value that said second electrode is moved with said first electrode by forces acting through said element at frequencies within a predetermined band in the operating range of the transmitter, the dimensions of said second passage being so proportioned and related that it offers a relatively high impedance to the passage of sound-pressure waves within a given frequency band in the operating range of the transmitter.

8. A transmitter comprising a hollow casing, a first movable electrode resiliently mounted within said casing, a second movable electrode resiliently mounted within said casing, a first chamberdefined in said casing adjacent said first electrode, a second chamber defined in said casing adjacent said second electrode, a first restricted passage formed in said casing and communicating between the exterior and said first chamber, whereby the movement of said first electrode may be controlled by sound-pressure waves, a second restricted passage formed in said casing and communicating between the exterior and said second chamber, whereby the movement of said second electrode may be controlled by sound-pressure waves, and a variable impedance element arranged between said electrodes, the effective impedance of said element being governed in accordance with the relative movement between said electrodes, the mass-stiffness of said second electrode and its resilient mounting being of such a value that said second electrode is moved with said first electrode by forces acting through said element at frequencies within a predetermined band toward the low frequency end of the operating range of the transmitter, the dimensions of said second passage being so proportioned and related that it offers a relatively high impedance to the passage of sound-pressure waves within a given band toward the high frequency end of the operating range of the transmitter.

9. A transmitter comprising a hollow casing including an annular side wall and top and bottrodes, said casing and said upper electrode being formed with said first-mentioned resilient mounting to provide an upper chamber above said upper electrode, said casing and said lower resilient mounting to provide a lower chamber 2,854,021 electrode being formed with said second-named I below said lower electrode, said casing having parts cooperating with said electrodes and said resilient means and said resilient mountings to form an annular chamber surrounding said electrodes, said casing having a passage forming a communication between said upper chamber and the exterior of saidfcasing, said casinghaving other passages forming restricted communications between theexterior of said casing and said annular chamber and between said annular chamber and said lower chamber.

10. A transmitter comprising a hollow casingincluding an'annular side wall and top and bottom walls, said bottom wall being insulated from said other walls, an upper electrode resiliently mounted withrespect to said top wall, a lower electrode resilientlymounted with respect to said bottom'wall, resilient means separating said electrodes, said casing and saidupper electrode be-- ing formed with said first-named resilient mountelectrode, said casing and said lower electrode being formed with-said second-named resilient mounting to provide a lower chamber below said lower electrode, said casing havingparts cooperating with said electrodes and said resilient means and said resilient mountings to form an annular chamber surrounding said electrodes, said cassaidcasing, said casing having other passages ing to provide an upper chamber above said upper oi. the upper chamber between the exterior'ot said casing and the annular chamber and between said annular chamber and said lower chamber, means for forming an electrical connection betweensaid casing d said upper electrode, and

means ior'forming an electrical'connection between said bottom wall and said lower electrode.

11. A transmitter comprising a hollow casing including an annular side wall and top and bottom walls, an upper electrode resiliently mounted with respect to said top wall, a lower electrode resiliently mounted-with respect to said bottom wall, resilient means separating said electrodes,

said casing and said upper electrode being formed with said first-mentioned resilient mounting to provide an upper chainber above said upper electrode, said casing and said lower electrode being formed with said second-named resilient mounting to provide a lower chamber below said lower electrode, said casing having parts cooperating with said electrodes and said resilient mean andv said resilient mountings to form an annular chamber surroundingsaid electrodes, said casing having a passage forming a communication between said upper chamber and'the exterior of a said casing, said casing having other passages ing having a passage forming a communication, between said upper chamber and the exterior of forming restricted communications between the exterior of said casing and said annular chamber and between said annular chamber and-said lower chamber, and a weight detachably secured to said lower electrode within said lower chamber; r ALBERT F. HORLACHER.

forming restricted communications independentlv 

